Top Benefits of 3D Printing Master Patterns for Urethane Casting

We often get asked if additive manufacturing will eventually replace traditional manufacturing technologies. Although we see companies migrating to 3D printing for complex geometries that can’t be built with traditional technologies and for advanced low-volume applications, we also see companies using it to complement and improve other manufacturing technologies. Cast urethane molding is one manufacturing process that is enhanced with 3D printing.

Urethane molding involves a silicone rubber mold to create polyurethane parts. First, you build a master pattern then pour liquid silicone around the master to create a mold. After the silicone hardens and the master is removed, you fill the mold with liquid polyurethane and place under heat and pressure to cure.

Pattern production is the most critical, time-consuming and costly step of the process. Masters are traditionally CNC machined out of wood, metal or plastic, which can take weeks and be very expensive for a throw-away part. As a result, companies are starting to produce master patterns with additive manufacturing, such as Fused Deposition Modeling (FDM), Laser Sintering (LS), Stereolithography (SL) or PolyJet for the following reasons:

Speed

3D printing master patterns accelerates the delivery date, especially if you’re working with a shop who offers both additive manufacturing and cast urethane services. You can reduce the pattern production time from a few weeks to a few days. It simply involves uploading the CAD design to the quoting engine, printing the part and sanding for a smooth surface finish, then sending it to the cast urethane shop.

Cost Savings

CNC machining a small, one-off master is a hard cost to justify. Also, a complex part design may require multiple set-ups and additional secondary operations, delaying production and costing more money. 3D printing can easily produce intricate design features without secondary operations or cost penalties because it builds parts from the ground up with removable support materials.

Complex Geometries and Surface Finish

3D printing gives you freedom to design complex master patterns with holes, organic shapes and channels not possible with CNC machining. It also opens the door to part consolidation in which multiple components can be combined into one part design to cut down on the number of molds. In addition, PolyJet can build in 16-micron layers to create very detailed, high-resolution parts. However, silicone molds have some limitations; for example, you need to be able to remove the rubber mold from hard to reach internal channels, so we recommend consulting a project engineer about specific design features.

Materials and Shelf Life

Most 3D printing processes offer silicone-compatible materials that can withstand heat and vacuum pressure throughout the casting process. However, a single master may be cast several times because silicone molds will usually last for 10 – 25 runs and average urethane orders are 100 – 1,000 parts. For long-lasting, durable masters for repeat orders, we recommend FDM. It uses engineering-grade thermoplastics which gives parts a long shelf life. Other additive manufacturing processes build simulated plastics that can warp over time.

Cast urethane molding is an efficient, cost-effective way to produce 100 to 1,000 end use parts in advanced formula polyurethanes. Stratasys Direct Manufacturing has refined its cast urethane process to apply additive manufacturing to master production, and has tested and certified a wide range of materials to deliver exceptional quality.

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